RX Qubit (Resonant Exchange)

Description

The resonant-exchange (RX) qubit is a three-electron, triple-dot spin qubit operating with always-on exchange and driven by RF modulation near the qubit splitting. It preserves exchange-only control while improving noise robustness compared with early exchange-only pulse sequences.

Figure

Hamiltonian

Low-energy effective qubit model:

$H=\frac{\hslash {\omega }_q}{2}{\sigma }_z+A_{\text{RF}}\cos ({\omega }_{d}t){\sigma }_x$

with ${\omega }_q$ set by static exchange couplings among the three dots.

Motivation

The RX qubit was designed to keep the control simplicity of exchange-only qubits while operating at a sweet-spot-like point where low-frequency charge noise is partially suppressed. By using resonant driving around a static exchange-defined splitting, it reduces reliance on large, abrupt pulsing sequences.

Key Findings

• Demonstrates coherent control in always-on exchange regimes.
• Provides a practical bridge between exchange-only and AEON-type operation.
• Compatible with resonator coupling proposals for long-range interactions.
• Highlights the speed/coherence trade space in three-spin encodings.

Key Metrics

Metric	Value	Notes	Fidelity reference
1Q gate fidelity	98–99.9%	Device dependent	Gyenis et al. 2021
2Q coupling path	exchange / resonator-mediated	architecture dependent	—
Operating temperature	20–100 mK	semiconductor dilution setups	—

Linked Papers

• medford-2013-rx-qubit

Related Entries

• exchange-only-qubit
• aeon-qubit
• singlet-triplet-qubit